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Regulatory mechanism of host cell contact-dependent T3SS gene expression in Vibrio parahaemolyticus

ABSTRACT: Many pathogenic bacteria have mechanisms that regulate gene expression in response to the surrounding environment to establish an infection. One such mechanism is the regulation of gene expression in response to contact with host cells. Here, we show that Vibrio parahaemolyticus, a causative agent of foodborne gastroenteritis, has a host cell contact-dependent regulatory mechanism for virulence gene expression. T3SS2, an essential virulence determinant for acute gastroenteritis encoded by V. parahaemolyticus pathogenicity island (Vp-PAI), recognizes host cell contact by sensing high intracellular K+ levels and switches its secretory substrates. This switching of secretory substrates is regulated by proteins called gatekeepers. Mutants deficient in the gatekeeper gene lose the ability to switch secretory substrates and lock their secretory state into contact with the host cell. Transcriptome analysis of T3SS2 gatekeeper gene-deficient strains showed that the genes encoded by Vp-PAI were specifically upregulated, and this upregulation was dependent on T3SS2 secretory activity, implying the presence of a negative regulator secreted by T3SS2. Comparative proteomic analyses identified a previously unidentified T3SS2 secretory substrate, VtrN, that negatively regulates Vp-PAI gene transcription. Secretion of VtrN was promoted under conditions that mimic host cell contact as well as other T3SS2 effectors. vtrN gene deletion specifically upregulated Vp-PAI gene expression, but unlike gatekeeper gene deletion, it was independent of T3SS2 secretory activity. Furthermore, VtrN interacted with VtrB, a transcription factor essential for Vp-PAI-encoded gene expression and repressed its transcriptional activity. Thus, V. parahaemolyticus has a mechanism to upregulate virulence gene expression in response to host-cell contact by utilizing the host-cell recognition mechanism of T3SS2.

ORGANISM(S): Vibrio parahaemolyticus

PROVIDER: GSE266863 | GEO | 2025/06/09

REPOSITORIES: GEO

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Project description:Vibrio parahaemolyticus is a Gram-negative marine bacterium. A limited population of the organisms causes acute gastroenteritis in humans. Almost all of the clinical V. parahaemolyticus isolates exhibit a beta-type hemolysis on Wagatsuma agar, known as the Kanagawa phenomenon (KP). KP is induced by the thermostable direct hemolysin (TDH) produced by the organism, and has been considered a crucial marker to distinguish pathogenic strains from non-pathogenic ones. Since 1996, so-called âpandemic clonesâ, the majority of which belong to serotype O3:K6, have caused worldwide outbreaks of gastroenteritis. In this study, we used a DNA microarray constructed based on the genome sequence of a pandemic V. parahaemolyticus strain RIMD2210633 to examin the genomic composition of 22 strains of V. parahaemolyticus, including both pathogenic (pandemic as well as non-pandemic) and non-pathogenic strains. Over 85% of the RIMD2210633 genes were conserved in all the strains tested. Many of variably present genes formed gene clusters on the genome of RIMD2210633 and were probably acquired through lateral gene transfer. At least 70 genes over 10 loci were specifically present in the pandemic strains when compared with any of the non-pandemic strains, suggesting that the difference between pandemic and non-pandemic strains is not due to a simple genetic event. Only the genes in the 80-kb pathogenicity island (Vp-PAI) on chromosome II, including two tdh genes and a set of genes for the Type III secretion system, were detected only in the KP-positive pathogenic strains. These results strongly suggest that acquisition of this Vp-PAI was crucial for the emergence of V. parahaemolyticus strains that are pathogenic for humans. Keywords: comparative genomic hybridization, CGH Total 66 test samples were analyzed. Genomic DNA from each test strain and a reference strain (RIMD2210633) were labeled with Cy3 and Cy5, respectively, and were cohybridized on a single array. Labeling and hybridization were performed three times independently.

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Regulatory mechanism of host cell contact-dependent T3SS gene expression in Vibrio parahaemolyticus

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